The CPC and the contributors to the Forecast Forum caution
potential users of this predictive information that they can expect only modest skill.

Discussion and Outlook

Cold episode (La Niña) conditions continued in the tropical Pacific during September.
Sea surface temperatures (SSTs) averaged more than 1°C below normal across the tropical
Pacific between 150°W and the South American coast, with weak negative anomalies
extending westward to 160°E (Figs. T9, T18).
Consistent with this, tropical convection [as inferred from anomalous outgoing longwave
radiation (OLR)] remained suppressed across the western and central equatorial Pacific
during the month (Fig. T25) and the low-level equatorial
winds remained stronger than normal across the same region (Fig.
T20).

The pattern of subsurface temperature anomalies has been highly persistent, with
positive anomalies in the western equatorial Pacific and negative anomalies farther east (Fig. T17). Consistent with this pattern, the oceanic
thermocline remained deeper (shallower) than normal in the western (eastern) equatorial
Pacific (Fig. T16). Over the last couple of months
temperatures at thermocline depth have decreased to more than 4°C below normal across the
east-central and eastern tropical Pacific. Also, the positive sub-surface temperature
anomalies in the west-central equatorial Pacific continue to show little evidence of an
eastward shift, indicating that cold episode conditions are likely to persist in the
tropical Pacific through the Northern Hemisphere winter 1999/2000. This assessment is
supported by the most recent NCEP coupled model forecast(Figs. F3 and F4)and by other available
coupledmodel and statistical model predictions that indicate cold episode
conditions persisting through the Northern Hemisphere spring of 2000.

Weekly updates of SST, 850-hPa wind and OLR are available on the Climate Prediction
Center homepage at: http://www.cpc.ncep.noaa.gov (Weekly
Update).